Introduced new osg::ObserverNodePath class that robustly manages a NodePath in a thread safe manner,

making it easier for users to track a NodePath even when nodes in the path get deleted.

include/osg/ObserverNodePath

@@ -0,0 +1,73 @@
+/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield
+ *
+ * This library is open source and may be redistributed and/or modified under
+ * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
+ * (at your option) any later version.  The full license is in LICENSE file
+ * included with this distribution, and on the openscenegraph.org website.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * OpenSceneGraph Public License for more details.
+*/
+
+#ifndef OSG_OBSERVERNODEPATH
+#define OSG_OBSERVERNODEPATH 1
+
+#include <osg/Node>
+#include <osg/Observer>
+#include <osg/ref_ptr>
+#include <list>
+
+namespace osg {
+
+typedef std::list< osg::ref_ptr<osg::Node> > RefNodePath;
+
+/** ObserverNodePath is an observer class for tracking changes to a NodePath,
+  * that automatically invalidates it when nodes are deleted.*/
+class OSG_EXPORT ObserverNodePath : public osg::Observer
+{
+    public:
+        ObserverNodePath();
+
+        ObserverNodePath(const ObserverNodePath& rhs);
+
+        ObserverNodePath(const osg::NodePath& nodePath);
+
+        ~ObserverNodePath();
+
+        ObserverNodePath& operator = (const ObserverNodePath& rhs);
+
+        bool valid() const { return _valid; }
+
+        void setNodePath(const osg::RefNodePath& nodePath);
+
+        void setNodePath(const osg::NodePath& nodePath);
+
+        void clearNodePath();
+
+        /** Get a thread safe RefNodePath.*/
+        bool getRefNodePath(RefNodePath& refNodePath) const;
+
+        /** Get a lightweight NodePath that isn't thread safe but
+          * may be safely used in single threaded applications, or when
+          * its known that the NodePath won't be invalidated during usage
+          * of the NodePath.*/
+        bool getNodePath(NodePath& nodePath) const;
+
+    protected:
+
+        void _setNodePath(const osg::NodePath& nodePath);
+
+        void _clearNodePath();
+
+        virtual bool objectUnreferenced(void* ptr);
+
+        mutable OpenThreads::Mutex      _mutex;
+        osg::NodePath                   _nodePath;
+        bool                            _valid;
+};
+
+}
+
+#endif

src/osg/CMakeLists.txt

@@ -111,6 +111,8 @@ SET(LIB_PUBLIC_HEADERS
     ${HEADER_PATH}/Notify
     ${HEADER_PATH}/Object
     ${HEADER_PATH}/observer_ptr
+    ${HEADER_PATH}/Observer
+    ${HEADER_PATH}/ObserverNodePath
     ${HEADER_PATH}/OccluderNode
     ${HEADER_PATH}/OcclusionQueryNode
     ${HEADER_PATH}/OperationThread
@@ -274,6 +276,7 @@ ADD_LIBRARY(${LIB_NAME}
     NodeVisitor.cpp
     Notify.cpp
     Object.cpp
+    ObserverNodePath.cpp
     OccluderNode.cpp
     OcclusionQueryNode.cpp
     OperationThread.cpp

src/osg/ObserverNodePath.cpp

@@ -0,0 +1,157 @@
+/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield
+ *
+ * This library is open source and may be redistributed and/or modified under
+ * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
+ * (at your option) any later version.  The full license is in LICENSE file
+ * included with this distribution, and on the openscenegraph.org website.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * OpenSceneGraph Public License for more details.
+*/
+
+#include <osg/ObserverNodePath>
+
+using namespace osg;
+
+ObserverNodePath::ObserverNodePath():
+    _valid(false)
+{
+}
+
+ObserverNodePath::ObserverNodePath(const ObserverNodePath& rhs):
+    _valid(false)
+{
+    RefNodePath refNodePath;
+    if (rhs.getRefNodePath(refNodePath))
+    {
+        setNodePath(refNodePath);
+    }
+}
+
+ObserverNodePath::ObserverNodePath(const osg::NodePath& nodePath):
+    _valid(false)
+{
+    setNodePath(nodePath);
+}
+
+ObserverNodePath::~ObserverNodePath()
+{
+    clearNodePath();
+}
+
+ObserverNodePath& ObserverNodePath::operator = (const ObserverNodePath& rhs)
+{
+    if (&rhs==this) return *this;
+
+    RefNodePath refNodePath;
+    if (rhs.getRefNodePath(refNodePath))
+    {
+        setNodePath(refNodePath);
+    }
+    return *this;
+}
+
+void ObserverNodePath::setNodePath(const osg::NodePath& nodePath)
+{
+    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
+    _setNodePath(nodePath);
+}
+
+void ObserverNodePath::setNodePath(const osg::RefNodePath& refNodePath)
+{
+    osg::NodePath nodePath;
+    for(RefNodePath::const_iterator itr = refNodePath.begin(); itr != refNodePath.end(); ++itr)
+    {
+        nodePath.push_back(itr->get());
+    }
+    setNodePath(nodePath);
+}
+
+void ObserverNodePath::clearNodePath()
+{
+    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
+    _clearNodePath();
+}
+
+bool ObserverNodePath::getRefNodePath(RefNodePath& refNodePath) const
+{
+    refNodePath.clear();
+
+    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
+    if (!_valid) return false;
+
+    for(osg::NodePath::const_iterator itr = _nodePath.begin();
+        itr != _nodePath.end();
+        ++itr)
+    {
+        refNodePath.push_back(*itr);
+    }
+
+    return !refNodePath.empty();
+}
+
+bool ObserverNodePath::getNodePath(NodePath& nodePath) const
+{
+    nodePath.clear();
+
+    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
+    if (!_valid) return false;
+    nodePath = _nodePath;
+    return !nodePath.empty();
+}
+
+void ObserverNodePath::_setNodePath(const osg::NodePath& nodePath)
+{
+    if (nodePath==_nodePath) return;
+
+    _clearNodePath();
+
+    _nodePath = nodePath;
+
+    for(osg::NodePath::iterator itr = _nodePath.begin();
+        itr != _nodePath.end();
+        ++itr)
+    {
+        (*itr)->addObserver(this);
+    }
+
+    _valid = true;
+}
+
+void ObserverNodePath::_clearNodePath()
+{
+    for(osg::NodePath::iterator itr = _nodePath.begin();
+        itr != _nodePath.end();
+        ++itr)
+    {
+        (*itr)->removeObserver(this);
+    }
+    _nodePath.clear();
+    _valid = false;
+}
+
+bool ObserverNodePath::objectUnreferenced(void* ptr)
+{
+    osg::Node* node = reinterpret_cast<osg::Node*>(ptr);
+
+    OpenThreads::ScopedLock<OpenThreads::Mutex> lock(_mutex);
+
+    _valid = false;
+
+    for(osg::NodePath::iterator itr = _nodePath.begin();
+        itr != _nodePath.end();
+        ++itr)
+    {
+        if (*itr == node)
+        {
+            _nodePath.erase(itr);
+
+            // return true as we wish calling method to remove self from observert set.
+            return true;
+        }
+    }
+    // return true as we wish calling method to remove self from observert set.
+    return true;
+}